P0a80 code: definitely means hybrid battery is bad?

I have had my 2007 Prius about a year now. It has about 138k miles on it. The other day the triangle light came on. Mechanic read the code and it said P0a80. He cleared the code. I drove home (a few miles) and parked the car. Next day triangle was back as soon as I started it. I cleared it with my own scan tool. Started driving. within a few miles triangle came back on. Parked the car at my destination. When I pulled over I noticed for the first time the fan by rear passenger side seatback blowing (seemed to be on high). Never heard that sound before or even knew there was a fan there.

My question is, does this code definitely mean the hybrid battery is bad or could there be another reason? For me it's a big decision as to whether to start spending money on this car. Are there other tests I should do before concluding that the hybrid battery is indeed bad? Any advice appreciated. Thanks.

Other electrical things going on prior to triangle warning:

In past month clock lost major time (hours) a few times.

In past 4 months dashboard would sometimes "go blank," i.e. no speedometer etc

In past 4 months sometimes car would not turn off. Took may tries to get it to turn off.

 

Thanks Bisco!

 

Had the batteries tested at Toyota. They told me the 12v battery is fine but the hybrid pack is bad. I decided to bite the bullet and get a new battery pack installed. It will be $2550 + tax. I thought about other options such as used battery or rebuilt. These options seem dicey. Now for the $2700 this car should last another 150k or 10 years.